Heat shock promoter sequences drive expression of an inverted repeat of Hr4 made by ligating two BspEI digested Hr4 cDNA fragments amplified using PCR primer GTTCGTCTAGAGACCGACAGATCTCGTACGAGCACGCC with TTGCTGTCCGGAGCCGCTCCGGGATCGTATCAGGACCAGG or TCTTCAAAATGGACGTGGATGCGGCTGAGG.